Social Networking backend architecture

Question

Ideally, where would an application like Facebook store its \"Friends\" data? In a database table? in an xml file?

Answer 1

"Friends" data is well-described in a graph database. Neo4j is an example, though I know it's not the way Facebook stores this information.

Facebook uses a number of database technologies that may be involved:

• a patched version of MySQL
• Cassandra
• Hadoop
• ... others